Effect of TCDD exposure on CYP1A1 and CYP1B1 expression in explant cultures of human endometrium

Endometriosis is a debilitating disease estimated to affect 10% of reproduc tive-age women and characterized by the growth of endometrial tissue outsid e of the uterus. The present study characterizes a human endometrial explan t culture model for studying the direct effects of TCDD exposure by assessi ng the expression of CYP1A1 and CYP1B1 mRNA (Northern blotting), protein (W estern blotting), and activity (7-ethoxyresorufln-O-deethylase; EROD) in ex plants cultured with and without TCDD. Explants were obtained at laparoscop y or laparotomy from women undergoing surgery for tubal ligation, endometri osis, or pelvic pain unrelated to endometriosis. The explants were cultured with 10 nM estradiol (E-2) or 1 nM E-2 plus 500 nM progesterone (P-4) with or without TCDD (first 24 h). The expression of CYP1A1 and CYP1B1 mRNA was greatest with 10 nM TCDD and increased up to 72 h after initial exposure. EROD activity increased up to 120 h. Explants from a secretory phase biopsy became reorganize in culture and formed a new epithelial membrane, while m aintaining basic endometrial morphology and viability for up to 120 h. At 2 4 h, TCDD significantly increased CYP1A1 and CYP1B1 mRNA, and at 72 h, TCDD significantly increased EROD activity and CYP1B1 protein compared to expla nts cultured without TCDD for similar times. CYP1B1 protein also exhibited substantial constitutive expression that was similar in uncultured biopsies , where CYP1B1 protein was immunolocalized in the cytoplasm of epithelial g lands, with only occasional patches of protein in the surface epithelia[ me mbrane. In explants cultured with and without TCDD exposure, CYP1B1 protein was localized in the cytoplasm of the new surface epithelial membrane and glands closest to the surface. CYP1A1 protein was not detected in unculture d biopsies or explants. Both younger age (age 30 and under) and proliferati ve phase were associated with higher TCDD-induced EROD activity in specimen s treated with E-2:P-4. No significant endometriosis-related differences we re observed for any of the biomarkers, but the detection of disease-specifi c change was limited by small sample size and variability in tissue-cycle p hase. The human endometrial explant culture model will be useful for future studies of the effects of dioxin-like,compounds on human endometrium in re lationship to cycle phase and hormonal exposure.